I just don't get why Joe Montana wants to be a part of selling a gimmicky shoe to the masses of people who are desperately grasping at any straw to "shape-up" and get fit. Sure, the shoes are probably no more harmful then the high heels many woman have already enslaved their feet to and lets face it walking around in 5 inch stilettos will build some serious calf muscles. However the muscle enhancement derived from wearing "Shape-ups", stilletos or any sort of footwear is just the bodies way of adapting to an unnatural way of walking which in turn can cause serious problems for other parts of the body ie. feet, back, knees.
The body is amazing the way it tries to compensate for whatever we humans decide to strap on our feet but in the end that overworked, "toned" muscle derived from wearing those ridiculous shoes is probably not good for much more then keeping one from toppling over in the silly things in the first place.